C-DATA
PON
What is PON?
A passive optical network (PON) is a system that brings optical fiber cabling and signals all or most of the way to the end user. Depending on where the PON terminates, the system can be described as fiber-to-the-curb (FTTC), fiber-to-the-building (FTTB), or fiber-to-the-home (FTTH).

Downstream signal coming from the central office is broadcast to each customer premises sharing a fiber. Encryption is used to prevent eavesdropping. Upstream signals are combined using a multiple-access protocol, usually time division multiple access (TDMA).

A PON consists of an optical line terminal (OLT) at the service provider’s central office (hub) and a number of optical network units (ONUs) orOptical Network Terminals (ONTs), near end users.
What is FTTH?
Since its promotion in 2003, FTTH has gone through 14 years. Since its launch in 2013, “Broadband China” has experienced another four years. FTTH has evolved from the dream of optical communications people to reality and has become a place where people work, study and live Indispensable infrastructure.

FTTH is an abbreviation for fiber optic directly to the home, abbreviated as FTTH in Chinese. Specifically, FTTH refers to installing an ONU at a home user or an enterprise user, and is an optical access network application type closest to a user except an FTTD (fiber to the desktop) in the optical access family. The significant technical feature of FTTH is that it not only provides more bandwidth, but also enhances the transparency of the network to data formats, rates, wavelengths and protocols, relaxes the requirements for environmental conditions and power supply, and simplifies maintenance and installation. When it comes to FTTH, you first have to talk about fiber access. Optical fiber access refers to the central office and users entirely between the optical fiber as a transmission medium. Optical access can be divided into active optical access and passive optical access. The main technology of optical subscriber network is optical transmission technology. At present, the multiplexing technology of optical fiber transmission develops quite fast, and most of them are in practical use. According to the depth of fiber users, can be divided into FTTC, FTTZ, FTTO, FTTF, FTTH and so on.
What is ODN?
ODN is an FTTH optical fiber network based on PON equipment, which provides optical transmission channel between OLT and ONU.From the perspective of function,ODN can be divided into four parts: feeder cable subsystem, distribution cable subsystem, inbound cable subsystem and fiber terminal subsystem.
What is ONU?
ONU consists of active Optical Network Unit and passive Optical Network Unit.It has two functions: selective reception of the broadcast sent by OLT, and receiving response to OLT if the data is needed;The Ethernet data that the user needs to send is collected and cached, and the cached data is sent to the OLT side according to the assigned send window.
How many kinds of ONU products you have?
ONU consists of active Optical Network Unit and passive Optical Network Unit. It has two functions: selective reception of the broadcast sent by OLT, and receiving response to OLT if the data is needed; The Ethernet data that the user needs to send is collected and cached, and the cached data is sent to the OLT side according to the assigned send window.
Does Your ONU can connect to the Phone and TV?
Yes.Our products have these functions.In particular, most of our ONU products also have WiFi capabilities.
What is the difference between GPON and EPON?
The main difference between GPON and EPON is the use of completely different standards.GPON was defined by ITU-TG.984 and EPON was defined by IEEE802.3ah.In application,GPON has a bigger bandwidth than EPON, its business carrying more efficient, spectral ability stronger, can transmit more bandwidth business, achieve more users access, pay more attention to business and QoS guarantee, but more complex, so cost is higher than its relative EPON , but with the large-scale deployment of GPON technology, EPON and GPON is diminishing cost differences.
What is the purpose of the LLID in EPON?
If the OLT (the central node of the EPON) were to be implemented as a PHY with a single MAC attached to it, this would cause serious trouble for any bridge (=switch) to which the MAC were connected. Consider a MAC frame coming into the bridge from an ONU (a subscriber node) via an EPON port. The bridge associates the source address of the frame with the port on which it came in, i.e. the EPON port. When at a later time another MAC frame comes in from an ONU, this time destined for the MAC address previously learned, it will not be transmitted back to the EPON port, because the bridge assumes that the frame was already received by all the stations on the attached “broadcast” LAN. However, this is not the case; upstream transmissions are not received by other ONUs. Standard bridging has no way of accomodating an attached LAN that behaves as a broadcast LAN in downstream and as a point-to-point LAN in upstream.

The solution to this problem was designed in close cooperation with Working Group 802.1. Instead of one single MAC, the OLT would have a different dedicated MAC for every ONU attached to the EPON. As a result, higher layers can consider the EPON as a collection of logical point-to-point links. From the individual MACs down to the OLT PHY, the logical point-to-point links share a common GMII; hence, a way to identify data frames for/from the different ONUs is required. The Logical Link identifier (LLID) was created for this purpose. The LLID is carried along by the frame in the bytes of its preamble.
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